Profile of a Tektite Researcher
Hal Povenmire is a tektite researcher from Ohio, USA. In July 2000, the main belt asteroid 12753 (which was discovered by Gene and Carolyn Shoemaker on April 18, 1993) was named in honour of Hal and Katie Povenmire for their many contributions to the International Occultation Timing Association (IOTA) and their studies and work in the field of meteors and meteorites.
He is the author of Fireballs, Meteors and Meteorites, Tektites, a Cosmic Paradox, Graze Observer's Handbook and has also published over 190 scientific articles.
Born in 1939, Hal has observed the Perseids for 54 consecutive years and has photographed over 2000 meteors. He is the discoverer of the Upsilon Pegasid Meteor Shower. Hal began mapping the Georgia Tektite strewn field in 1970, increasing its known size from 500 square miles to over 8000 square miles. He has worked on the Baker-Nunn Satellite Tracking Cameras for Project Moonwatch, worked on Project Mercury and Project Apollo and has also worked with the press corps at the Kennedy Space Center. Some of his engineering work still sits on the Sea of Tranquility from the Apollo 11 Mission.
Hal has served as the Assistant Director of the American Meteor Society coordinating fireball work and meteorite recovery, and originated the Florida Fireball Patrol which has grown to be the fourth most successful fireball network. Hal owns the second largest meteorite research collection in the southeastern United States. He has taught astronomy in the Cape Canaveral area, was director of the Satellite Beach Observatory and the Bishop Observatory, as well as the planetarium at the Museum of Arts and Sciences in Daytona Beach, Florida.
Hal has postgraduate qualifications in astronomy, space science and space technology, but considers himself "just a farm kid from Ohio who happened to get turned on by rockets!"
The Lunar Volcanic Theory of Tektites
Tektites are small glassy natural objects of uncertain origin found on Earth, which have made at least one trip through the atmosphere. Tektites are found in groups with similar characteristics in fields or areas called strewn fields.
Although all planetary scientists are in agreement that tektites originated within the Earth - Moon system, there are two major theories as to their origin, the most popular, simplest and widely accepted is that they are the result of a terrestrial impact caused by a comet or asteroid throwing material out into space that reentered as 'Tektites'.
The second theory is that tektites are Lunar Obsidian the result of lunar volcanic ejecta, which escaped lunar gravity and fell onto the Earth.
To support the first theory of formation by terrestrial impact, there must be a crater corresponding to each fall. Craters have been found for the falls of 65 million years (my), 35my, 15my, and 1.1my ago. However the most recent fall, (the Australasian fall: .78 million years ago) does not have any known corresponding crater. This crater would be found in the Indochina area and have a diameter of approximately 80 miles. In spite of a great deal of fieldwork, no crater has yet been found.
Apollo 11 was expected to find vast quantities of tektites on the Moon, yet did not. However, when we used the electron microprobe on the small volcanic spherules that make up the regolith of the Moon, we found them to be identical to the composition of tektites! (An excellent web page: info on the Moon.)
Two small spheres of glass (about the size of a pea) were recovered by Apollos 12 and 14. The Apollo 14 specimen (14425), when analyzed under the electron microprobe, showed a composition essentially identical to some Australasian Tektites; so identical, in fact, that if this specimen had been found on the Antarctic ice shelf instead of Fra Mauro, it would have been declared a tektite!
During the Apollo era, 843 pounds of lunar rocks were recovered and brought back to Houston for analysis. About 10 years later, a small meteorite found in Antarctica, named Allan Hills 81005, was found to be of lunar origin. Since then about 24 other lunar meteorites have been recognised coming from Antarctica, Australia and Africa. It should be noted that these are lunar meteorites ejected into space and fallen back to Earth. (It has been calculated that a one-pound meteorite hitting the Moon can eject 4 pounds of lunar material into space, some of this reaching Earth.)
The strongest evidence of the second theory of tektite formation comes from basic physics. Stokes' Law deals with the way that a bubble rises in a liquid. The rate of rise is directly proportional to the heat, pressure and viscosity of the liquid. Glass is a liquid that follows these laws and may form in one of two ways. The first is like that of an impact or shock. When sand is subjected to an intense shock it forms a crude glass. This can occur when lightning, an artillery shell or a meteorite impacts sand. The temperature rises very quickly, melting the sand and then freezes it very quickly not allowing any fining or homogenisation to occur. This is referred to as shock or impact glass.
The second form of glass is that of fined or homogenised glass. This requires careful heating in a crucible over a period of time to allow bubbles to rise and for the glass to become homogenised. This type of glass is found in three situations: artificial glass, obsidian, and in tektites.
Professional glassmakers, such as Corning, make extremely high quality glass following Stokes' Law. Sand is heated and kept at a high, stable temperature usually for about 16 hours. Certain temperatures must not be exceeded or volatiles will evaporate resulting in substandard glass. This same procedure occurs in erupting volcanoes, giving us obsidian or volcanic glass. We know that tektites have undergone a similar process occurring outside of the Earth's atmosphere. The closest place where volcanic activity occurs is the Moon. If we heated silica dioxide in an anhydrous crucible such as a lunar volcano, we would obtain glass, which is essentially devoid of water. Tektites are extremely dry glass typically containing approximately 40 parts per million of water while terrestrial obsidian contains approximately 4000 parts water per million.
Some planetary scientists have argued that the Moon is geologically dead. I do not believe this to be true. The source of heat is the radioactive decay of Uranium and Thorium. (There is also minor seismic activity on the Moon.) If planetary scientists expect to reject the lunar volcanic ejecta theory of tektites then they would have to prove Stokes' Law (a law that has been known over 100 years!) to be incorrect. They must also find a large crater in the Indochina area, for which we have searched for over thirty years. With what we now know, formation of tektites by impact is impossible due to Stokes' Law.
The Story of Asteroid (12753) Povenmire
In 1982, Eugene and Carolyn Shoemaker started working on the Palomar Asteroid and Comet survey (PCAS) using the 18" Schmidt on Palomar Mountain. The purpose of this survey was to search for comets and near earth asteroids (NEO). On the night of April 18, 1993, a fairly bright main belt asteroid was photographed. It was tracked long enough to be given the preliminary designation 1993HE.
In the following years it was followed through 5 oppositions and the orbital elements were well determined. This asteroid has an H or absolute magnitude of 12.5. (The absolute magnitude is how bright the asteroid would be when it is one astronomical unit (A.U.) from the Earth and from the Sun.) This would suggest that if this asteroid is of normal reflectance, or albedo, that it is probably about 9 miles in diameter.
It comes to opposition about every 15 months and can reach about 15 magnitude under favorable conditions. This is bigger and brighter than most new asteroids being discovered today. At the closest point to the Sun (perihelion), it lies at a distant of approximately 2.2 astronomical units (AU). (An AU is the average distance from the Earth to the Sun or about 93 million miles.) At its farthest point or aphelion, it has about 3,010 AU.
This main-belt asteroid moves in an elliptical or egg-shaped path around the sun taking approximately 4.3 years to complete one revolution. It never gets as close to the Sun as Mars or as far out as Jupiter.
Since this asteroid has been in the main belt since the solar system started some 4.6 billion years ago, it is probably very battered by collisions with other asteroids. It may have originally been much larger. It is probably of stony or silicate composition with a specific gravity of about 3.5. Most asteroids have a somewhat inclined orbit to the ecliptic.
On August 4, 2000, Carolyn Shoemaker formally announced the name of this asteroid as (12753) Povenmire. A ceremony was held in Houston, Texas, and was attended by Hal and Katie Povenmire.
Meteor Researcher: John A. O'Keefe
by Hal Povenmire
John O'Keefe was born in Lynn, MA., October 13, 1916. He received his A.B. degree from Harvard in 1937 (Magna Cum Laude) and married Martha Sylvia Tulane from William's Bay, Wisconsin, in August 1941. They have nine children and 25 grandchildren.
O'Keefe became professor of mathematics and physics at Brenau College in Gainesville, Georgia. After Pearl Harbor, he took a position with the U.S. Army Corps of Engineers. He was chief of the research and analysis Branch, US Map Service from 1945 to 1958. During this time he and his team invented the UTM coordinate system, aiding in the accuracy of our weapons systems. From this position, O'Keefe joined NASA in 1958 and continued his career in astronomy and space sciences.
Working with the Vanguard and Explorer teams with Wernher von Braun, he determined the pear-shaped nature of our Earth from the deviation in the orbits of our early satellites. He also did significant research in improving the values for the velocity of light.
O'Keefe has authored one major book and edited two others; one dealing with the surface of the Moon and two on the mysterious small glassy meteorites called Tektites. Attempting to determine the origin of these objects has been a major effort. He advocated volcanoes on the Moon as their source. Perhaps some of his greatest work has been to be the worthy opposition to many of the commonly accepted flawed hypotheses on this subject. While the origin of Tektites has not been proven nor disproved, it has forced great minds to apply themselves to this enigma.
On May 27, 1997, the American Geophysical Union honored him with a retirement ceremony in Baltimore, MD. Eugene Shoemaker presented him with an asteroid now known as (6585) O'Keefe. John O'Keefe's passing on September 8, 2000, was a great personal loss as he was my teacher, mentor and friend.
Author: Lydia Lousteaux